本文選題：贛南　切入點：富城巖體　出處：《南京大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：本文研究的珠蘭埠花崗巖和富城花崗巖分別位于贛南會昌地區(qū)會昌盆地東西兩側(cè)。其中富城巖體西部與橄欖玄粗巖系列火山巖接觸,河草坑鈾礦田就產(chǎn)于該花崗巖體的內(nèi)外接觸帶。作為礦床圍巖的富城巖體西部花崗巖中發(fā)育大面積的蝕變帶,在宏觀上表現(xiàn)出“上紅下綠”的特征。為了深入探討本區(qū)蝕變與鈾礦化的關(guān)系,本文運(yùn)用電子探針技術(shù)對該蝕變帶中的黑云母及其蝕變產(chǎn)物綠泥石進(jìn)行了礦物化學(xué)對比研究。結(jié)果表明,富城巖體中黑云母屬鐵葉云母,黑云母鋁鐵鎂組分的特征符合過鋁質(zhì)S型花崗巖的特點,可推斷其源區(qū)物質(zhì)主要來源于地殼沉積巖；根據(jù)黑云母成分估算的富城花崗巖巖漿的氧逸度較低(1g(fO2)值約為-15.0～-14.3),表明該花崗巖的源巖具有較強(qiáng)還原性,有利于鈾在源區(qū)沉積巖中的富集；富城巖體U含量在13 ppm以上,遠(yuǎn)高于世界花崗巖的平均鈾含量(3.5 ppm)；花崗巖中黑云母的氟含量達(dá)1.41～2.01wt%,表明該花崗質(zhì)巖漿富F,而富F巖漿中U溶解度高,可能是富城巖體富鈾的重要原因之一。黑云母常被綠泥石交代,呈黑云母假象。綠泥石礦物化學(xué)分析結(jié)果表明,綠泥石以鮞綠泥石和蠕綠泥石為主,屬于富鐵的綠泥石,主要形成于還原環(huán)境；綠泥石的形成溫度介于246～307℃之間,平均276℃。此外,通過顯微鏡下特征等的對比分析,查明下部綠色蝕變層主要由綠泥石化產(chǎn)生,為還原環(huán)境蝕變產(chǎn)物；上部紅化蝕變層則是較晚期赤鐵礦化的結(jié)果,為氧化環(huán)境蝕變產(chǎn)物。全巖U、Th含量分析結(jié)果表明,上部紅化蝕變層U含量(3.5～9.4 ppm,平均6.6 ppm)明顯低于下部綠色蝕變層(7.7～23.1 ppm,平均13.9 ppm),而紅化蝕變層與綠色蝕變層的Th含量基本相似,其平均值分別為35.7 ppm和36.5ppm。而富城復(fù)式巖體未蝕變的新鮮巖石平均U含量為22.5ppm(任海濤,2013),可見礦前期的帶狀大體積面型綠色蝕變活化了礦物晶格中的結(jié)構(gòu)鈾,鈾發(fā)生部分轉(zhuǎn)移；成礦期高氧逸度的流體萃取綠色蝕變層中已經(jīng)活化了的鈾而形成含鈾成礦熱液,同時形成了以赤鐵礦化為主的紅化蝕變層,含鈾流體中的六價鈾可能主要以氟合鈾酰離子(UO2F42-和UO2Fs-)及鈾酰氟化物(UO2F2)的形式遷移,在綠色層和紅色層的氧化還原界面部位沉淀成礦。這可能是富城巖體西部蝕變帶中的花崗巖型鈾礦體多產(chǎn)于紅化蝕變和綠色蝕變的接觸部位的原因。Th的價態(tài)(正四價)很難隨氧化還原條件而改變,因此未參與流體成礦過程。此外,巖石氧化還原電位測試結(jié)果顯示綠色蝕變層巖石的還原性最強(qiáng),隨著紅化蝕變的加強(qiáng),巖石的還原能力減弱,這為上述成礦過程提供了佐證。富城花崗巖的活動鈾浸出率平均為52%(任海濤,2013),綠色蝕變層的活動鈾浸出率平均為30%,而紅化蝕變層的活動鈾浸出率平均僅為8.6%,這暗示富城花崗巖活動鈾浸出率很高,存在很大的成礦潛力,綠色蝕變層的活動性鈾已經(jīng)部分遷出,而紅化蝕變層的活動性鈾幾乎完全遷出。這些遷移的鈾可能是河草坑鈾礦田成礦所需鈾的來源。為了深入研究富城西部產(chǎn)鈾花崗巖體蝕變帶的地球化學(xué)特征,本文選擇會昌白堊紀(jì)斷陷紅盆北側(cè)珠蘭埠花崗巖體進(jìn)行對比研究,從年代學(xué)、地球化學(xué)特征以及產(chǎn)鈾潛力等方面揭示會昌斷陷紅盆兩側(cè)花崗巖體鈾成礦作用的差異性。研究表明,珠蘭埠花崗巖形成于225～228Ma左右,年齡與富城巖體相近,為印支期花崗巖。珠蘭埠花崗巖具有S型花崗巖的巖石學(xué)和地球化學(xué)特征。樣品具有高Si、Al特征,鋁飽和-過飽和,K20/Na2O比值大于1.2,Ca、Mg含量低,具有較高的Rb、Th、U等大離子親石元素,虧損Sr、Ba、Eu等元素,Ga/Al比值和Zr+Nb+Ce+Y含量較低。εHf(t)介于-7.7～-12.9之間,平均為-9.7；兩階段Hf模式年齡介于1.74～2.06Ga,平均1.87Ga；兩階段Nd模式模式年齡為1.65～1.80Ga,εNd(t)介于-7.9～-9.8,平均為-9.0；(87Sr/86Sr)i值介于0.7156～0.7264之間。綜合巖相學(xué)和地球化學(xué)特征分析,認(rèn)為珠蘭埠花崗巖來源于古元古代地殼富泥質(zhì)組分,在板塊碰撞加厚期后的應(yīng)力舒張階段,發(fā)生部分熔融而形成的印支期S型花崗巖。珠蘭埠巖體U含量(平均為10.9ppm)雖然高于中國東部上地殼平均值(1.5ppm,高山等,1999),但明顯低于東部富城復(fù)式巖體平均U含量(22.5ppm,任海濤,2013)。且珠蘭埠巖體活動鈾元素浸出率(平均為25.7%)也遠(yuǎn)低于富城巖體(平均為52%,任海濤,2013),表明珠蘭埠巖體的活動性鈾含量低,且珠蘭埠巖體蝕變和構(gòu)造相對均不發(fā)育,不利于成巖后鈾元素的遷移成礦。
[Abstract]:This paper studies the zhulanbu granite and Fucheng granite are located in the Huichang area of the Huichang basin. The East and west sides of Fucheng pluton Western contact with shoshonitic volcano rock, inner and outer contact zone of Hecaokeng uranium ore field is produced in the granite. As the development of a large area of the granite rock deposit Fucheng pluton in the alteration zone, characterized by "green" red in the macro. In order to discuss the relationship between the alteration and uranium mineralization, using biotite and etching electron probe technology of the alteration zone in the product of chlorite were studied. The results show that the mineral chemical contrast, Fucheng pluton in the clouds the mother is siderophyllite, biotite characteristics of aluminum iron and magnesium components in accordance with the characteristics of aluminous S type granite, it can be concluded that the source materials are mainly derived from the crust sedimentary rocks; according to the estimation of biotite composition Fucheng The granite magma of the low oxygen fugacity (1g (fO2) is about -15.0 ~ -14.3), indicates that the source rocks of the granite has strong reducibility, is conducive to the enrichment of uranium in the source region of sedimentary rocks; Fucheng pluton U content is over 13 ppm, far higher than the world average uranium content of granite (3.5 ppm); fluorine content in biotite granite in 1.41 ~ 2.01wt%, shows that the granitic magma rich in F and F rich magma U high solubility, may be one of important reasons for Fucheng uranium rich rock. Biotite chlorite is often explained, is biotite chlorite illusion. Chemical analysis results show that the chlorite chamosite and aphrosiderite mainly belong to the Fe rich chlorite, mainly formed in the reducing environment; formed between the temperature between 246~307 DEG C chlorite, average 276 degrees. In addition, by comparing the microscopic characteristics of the analysis, find out the lower layer is mainly composed of green green alteration Chloritized, for reducing environment alteration products; the upper red alteration layer is relatively late hematitization results for oxidizing environment alteration products. The whole rock U, Th analysis results show that the content of the upper layer of red altered U content (3.5 ~ 9.4 ppm, average 6.6 ppm) was significantly lower than that under green alteration layer (7.7 ~ 23.1 ppm, average 13.9 ppm), and the content of Th alteration layer and green alteration layer are similar, the average values were 35.7 ppm and 36.5ppm. and the average U content of urban complex rock mass without alteration of the fresh rock is 22.5ppm (Ren Haitao, 2013), visible the large volume type ore belt green alteration was activated in the lattice structure of uranium minerals, uranium partial transfer; extraction of high oxygen fugacity mineralization green alteration layer have been activated uranium and uranium metallogenic hydrothermal formation, while the formation of red hematite mineralization alteration to the layer containing. Six the price of uranium in the fluid may be the main fluoride uranyl ions (UO2F42- and UO2Fs-) and uranyl fluoride (UO2F2) in the form of migration, reduction in oxidation layer and the interface part of the green red layer deposits. This is probably the valence of.Th causes contact parts of granite type uranium deposits in Fucheng pluton in the alteration zone the red body prolific in the alteration and the alteration of the green (positive tetravalent) is very difficult with the redox conditions changed, so did not participate in the ore-forming process. In addition, the rock redox potential test results show that the reduction of the strongest green alteration rock, with the strengthening of red alteration, reduced the ability of rock, which provides evidence for the ore-forming process. Activities of Fucheng granite uranium leaching rate averaged 52% (Ren Haitao, 2013), activity of uranium leaching green alteration layer for the average rate of 30%, while the activity of uranium leaching alteration of red layer average rate 8.6%, suggesting that the activity of Fucheng granite uranium leaching rate is very high, there is great potential for metallogenic activity of uranium, green alteration layer has been partially moved, and the activity of the uranium red alteration layer almost completely out of uranium migration. These may be a source of Hecaokeng uranium mineralization of uranium. In order to required study of uranium granites in western urban alteration geochemical characteristics, this paper chooses Huichang Cretaceous faulted red basin of North zhulanbu granite were investigated from the chronology, reveals Huichang down faulted basin on both sides of granite uranium mineralization differences in geochemical characteristics and uranium metallogenic potential. Research shows that zhulanbu granite formed in 225 ~ 228Ma, and the age of Fucheng pluton is similar to Indosinian granite. Petrology and earth zhulanbu granite with S type granite. The chemical characteristics of samples with high Si, Al The characteristics of aluminum, saturated and supersaturated, K20/Na2O ratio is greater than 1.2, Ca, low Mg content, high Rb, Th, U and other large ion lithophile elements, Ba, loss of Sr, Eu and other elements, the ratio of Ga/Al and Zr+Nb+Ce+Y were low. Epsilon Hf (T) between -7.7 ~ -12.9, average -9.7; two stage Hf model between the ages of 1.74 ~ 2.06Ga, average 1.87Ga; two stage Nd model age of 1.65 ~ 1.80Ga ~ Nd (T) from -7.9 to -9.8, the average is -9.0; (87Sr/86Sr) I value between 0.7156 and 0.7264. Comprehensive analysis of petrographic and geochemical characteristics, think Zhu LAN Bu granite from the Paleoproterozoic crustal mud rich component in stress relaxation phase plate collision thickening stage after the partial melting and the formation of the Indosinian S type granite. Zhulanbu rock U content (average 10.9ppm) is higher than that of average China in the upper crust (1.5ppm, alpine, 1999). But obviously lower than that of the East The average U content of urban complex (22.5ppm, Ren Haitao, 2013). And zhulanbu rock activity of uranium leaching rate (average 25.7%) is far lower than that of Fucheng pluton (the average is 52%, Ren Haitao, 2013), the activity of the uranium content of the Pearl LAN Bu rock, and zhulanbu rock alteration and relatively are not developed, is not conducive to the migration of uranium mineralization into rock.

【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P588.121;P619.14

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